How can I add a text behind an image in IText7 c#?

Question

I am generating a pdf from others with IText7 in C# and I need to add information in a corner of each page automatically, I add the information but in some pages, the content occupies the entire page and I need the information to be left behind in those cases of the content, I attach the image of the result, thanks in advance

I am using a canvas and Div to add the text

PdfPage pag = pdfDocument.GetLastPage();
Canvas canvas = new Canvas(pag, pag.GetPageSize());
var div = new Div().SetMargin(0).SetPadding(0).SetKeepTogether(true);
div.SetFixedPosition(0, 0, pag.GetPageSize().GetWidth());
div.Add(new Paragraph("info").SetFontSize(12));
canvas.Add(div);
canvas.Close();

Sorry my English

result: Pdf text added result

expected: Pdf text added Expected

Answer 1

I have found the solution, I create a PDFCanvas and indicate that NewContentStreamBefore(), and it already adds the information behind the page

PdfPage pag = pdfDocument.GetLastPage();

PdfCanvas under = new PdfCanvas(pag.NewContentStreamBefore(), pag.GetResources(), pdfDocument);

Canvas canvas = new Canvas(under, pag.GetPageSize());
var div = new Div().SetMargin(0).SetPadding(0).SetKeepTogether(true);
div.SetFixedPosition(0, 0, pag.GetPageSize().GetWidth());
div.Add(new Paragraph("info").SetFontSize(12));
canvas.Add(div);
canvas.Close();